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Study: Some Extra Weight OK After All

FILE - Gym members use treadmills to warm up for a morning exercise class at Downsize Fitness, in Addison, Texas, Jan. 3, 2013. Researchers in Denmark found that carrying a few extra kilograms might not be as harmful as it was a few decades ago.

Researchers in Denmark say it may be time to add a few kilograms to the scale that charts our optimal weight.

They've done new research suggesting that carrying a bit of extra weight is less dangerous now than it was 40 years ago.

The surprising results came from a study that looked at mortality rates, and compared them to people's body mass index.

BMI not what it used to be

Also called BMI (body mass index), the index is a ratio of a person's height to their weight, and doctors use it to gauge a healthy weight range.

A BMI of between 18.5 and 24.9 is considered healthy. Between 25 and 29.9 is overweight, anything over that is in the obese range.

In the 1970's, the optimal BMI - that is the number that had the fewest deaths associated with it - was 23.7. That corresponds to a 1.83 meter man weighing 77 kilograms, or a 1.65 meter woman who checks in at 65 kilograms.

But in this new study, the doctors found that the optimal BMI has been steadily moving up.

In 1994, the optimal BMI was up to 24.6, and by 2013, it had shot up to 27.

That means today, the most healthy 1.83 meter man is carrying 14 kilograms more than he did in the 70's, and a 1.65 meter woman, an extra 9 kilograms.

It's not the weight, it's the math

That's good news for anyone who is struggling to reach that optimal BMI.

But the results have scientists scratching their heads. The study, printed in this week's Journal of the American Medical Association only says, "Further investigation is needed to understand the reason for this change and its implications."

That's science parlance for "we have no idea."

The other big news out of the study is that people classified as obese are now no more likely to die than people within the normal weight range. Forty years ago, an obese person was 30 percent more likely to die than a person of normal weight. Today, at least in Denmark, that percentage has dropped to zero.

The authors are quick to point out that this doesn't mean people should stop eating nutritious food and watching their weight, and that much more research is needed to understand the study’s results.